There existed various kinds of indirect system spot welding machines for welding hemming portions of an automobile door or the like. However, such conventional indirect system spot welding machines have been said to have a drawback resulting from remaining some pressed traces caused by pressing the spot electrode to the work (pressed product). It has been requested to eliminate such a drawback of pressed traces. Also, there is a problem connecting the secondary earth cable of the welding transformer to the work side.
In conventional system, a particular jig was provided in the material handling side to fix the work at a predetermined position. While, an earth cable is always connected at jig side. Further a back bar is fixedly provided to outside surface of the work, and the back bar accepts the pressure of the spot electrode from the welding side.
Accordingly, workability of the particular jig is limited, thus construction cost is adversely increased. Further, the amount of the earth cable wired at secondary side is increased and freedom of space utility in the circumference of the spot welding machine is considerably restricted. The useful life of the earth cable is thus shortened.